Hello again!
Explanation:
The two balloons will start at the same height, 800. The first balloon, however, descends at a slower rate than the third balloon, as we can see by substituting Y for zero. the first takes 40 seconds, but the third one takes about 27 seconds, while starting at the same height. Graphically, this means that the third balloon will reach the x axis first, and the line will be steeper, as the slope of the third balloon is greater than the slope of the first one (-30 is steeper than -20)
;)